How to tell if wired client is active in DHCP?

For wireless clients, when they disconnect, they change interface (from devices list) from eth1 to br0. However, for wired clients, it stays as br0 whether it's connected or not. (Also, wireless clients show a signal quality when connected).

Hmm.. i have all computers in Device List and WakeOnLan list when they are turned on and when they are turned off. I check them with ping to see is computer turned on/off, but problem is when some computer is in Stand By mode, specific computer is not in use, but ping reply is ok

Device list shows which computers still have a lease, so there's nothing wrong with that. Maybe an extra "Active" column with a tick if in WOL list might be a nice addition. Or even combine the two ...

The device list uses the arp table (cat /proc/net/arp) to determine what devices are connected. Dynamic devices hang around in that table for about 5 minutes before dropping out. WOL uses "magic packets", sent to the machines Ethernet card MAC address. If you want to wake a machine by static IP address it needs to have a static arp assignment to link IP and MAC, and it must be this that fools the device list.